Explosive



oxygen carrier, such as Patented Nov. 9, W43

EHLOSIVE No Drawing.

Bronxville, N. Y.,

assignor to Application August 17, 1939, Serial No. 290,630. In CanadaFebruary 18, 1938 11 Claims.

The present invention relates to explosive compositions of the type inwhich an absorbent carrier is used.

The so-called dynamites, permissible explosives and the like, usuallyconsist of a liquid explosive component such as nitro-glycerine,nitro-glycols, or other nitrated bodies, together with an explosive saltsuch as ammonium nitrate and/or an sodium nitrate, sodium and potassiumchlorate and sodium and potassium perchlorate, together with anabsorbent, In some instances, absorbents of the diatomaceous earth typeare used. In these cases, the absorbent is entirely inert, that is, itcontributes nothing toward the eventual explosion. For this reason, acarbonaceous -combustible material is preferred as the absorbent.absorbents are usually of vegetable origin, such as plant tissues andsuch substances as ground cork, bagasse pith, balsa wood, wood flour,sawdust, corn flakes, popcorn and the like, have been proposed.

One characteristic feature of these heretofore used absorbents is thattheir porosity is uniform throughout, although the relative porosity ofthe various materials difiered. Inasmuch as there wasno way ofmodifyingthe porosity of a particular absorbent, a the above group byreason of its porosity factor occurring as near the desired point aspossible. This naturally excluded from use many materials otherwisedesirable.

It is important in explosives of the straight dynamite type where aliquid explosive compound such as nitro-glycerine is absorbed in acarrier, that the absorptive power of the carrier be such as to preventexudation of the liquid explosive or segregation thereof in the packageafter manufacture.

Another important desideratum in the choice an absorbent is that if itis combustible, its chemical composition must be such that it will notupset the carbon-oxygen balance during combustion so as to leave greaterthan permissible quantities of carbon monoxide in the space followingthe explosion. Not all of the materials which otherwisermeet thenecessary qualifications as an absorbent, have these characteristics.

For certain operations, it is desirable to have a comparatively largevolume of explosive without, however, increasing the weight thereof orthe disruptive force of the explosive charge. In such cases, explosivessired. For this reason, some absorbents are preferred over othersbecause of their low density.

These carbonaceous material was chosen fromsuch, for instance, asbagasse pith, balsa wood, sphagnum moss and the like. One of thedifficulties, however, with these fillers of exceptionally low densityis that they have high absorptive power and, consequently, they eitherhave a tendency to absorb too much of the liquid explosive or, if lesserquantities of the latter are used, the explosive propagation rate islowered below a desirable limit.

Another important consideration from the standpoint of explosivescontaining nitroglyce erine is that in order to effectively initiate theexplosion, a considerable quantity of the nitroglycerine must beinstantly available to the detonator, that is, at the surface of theabsorbent. Some absorbents, such as balsa and bagasse are bad from thisstandpoint because the nitroglycerine is completely contained within itspores and none remains on the surface of the cell Walls.

As a consequence, the combination is more insensitive than wouldordinarily be desired.

Generally speaking, the ideal absorbent must be capable of absorbinglarge quantities of the explosive, where the explosive is of thenitroglycerine type it must be capable of leaving some of that substanceat the surface, the absorbent must be capable of holding a liquidexplosive without segregation or leakage, the absorbent must be stableand incapable of developing an acid or an alkaline reaction, forpermissive ex plosives the absorbent must give a low density stick, thecarrier should have a minimum amount of inerts which would show up asmineral ash while at the same time, the absorbent must be of acarbonaceous nature and capable of being burned during the explosion,without, however, disturbing to a marked degree the oxygen balance ofthe explosive composition. Another very important consideration is theability to produce the carrier or absorbent having various sizes ofpores therein. These pores may be uniform throughout the mass or theymay vary within a single mass, as desired.

It has been discovered that the above properties are met to a maximumdegree by artificially produced porous, carbonaceous masses made fromplastics capable of having its degree of porosity controlled.

of a low density are de- I The present invention aims to overcome theabove deficiencies by providing an absorbent which meets all of thedesirable conditions, which has none of the undesirable characteristics,the porosity of which may be controlled during its manufacture to anydesired point, even to the point of being modified in different parts ofits bulk, which is readily combustible in and of itself and which, underthe influence of the high temperatures usually attendant the explosion,W111 itself decompose or oxidize more readily than other absorbentsheretofore used.

hyde condensation product in a dispersed form,

and removing the dispersing medium under such conditions that thecollapse of the particles either can be prevented or regulated to form aporous gel. The porosity of the product may be regulated by regulatingthe temperatures attendant upon the removal of the dispersing medium.The production of products where the absorption varies on the same piececan be made principally in two different ways: either the jelly isheated to a higher temperature during the production, before thestructure is solidified thoroughly, in which case the outer layer willcollapse more or less, dependent upon temperature and humidity; or thefinally hardened jelly is impregnated with water or aqueous solutionsand quickly heated to a high temperature, whereby the outer layercollapses, whereas the inner part remains unchanged.

-An example of solid material as above produced has an apparent densityof about 0.5 and on heating, decomposition commences at about 150 C.There is no melting point. The porous product has been found to have theability of absorbing, approximately twice its weight in water.Nitro-glycerine (20% polymer) may be absorbed by the porous material inthe form of a block in an amount equal to about twice the weight of theblock. This value, of course, will vary with the viscosity of thenitro-glycerine. This absorption value corresponds to approximately 66%.The usual wood pulps have absorption values in the neighborhood of 'IOto78% whereas balsa or bagasse may reach 85%. This condensation product isinert to alkali or alkaline earths encountered in explosive manufacture.These properties may be made to vary over rather wide limits by varyingthe method of production.

Moreover, the finished product may be ground to the desired degree ofparticle size where porosity is not particularly important and it isdesired to take advantage of the desirable characteristics of thechemical composition of such condensation products as an explosiveingredient.

These condensation products also have the parti'cular advantage of beingable to be produced in any desired shape.

Such a porous gel may be prepared by condensing urea and an'aqueoussolution of form-' aldehyde in a ratio of 1 mol. of urea to two mols. offormaldehyde in a reflux apparatus. At the beginning of the condensationprocess, the solution should be maintained at a pH value of '7 orhigher. After fifteen minutes of condensation, formic acid may be addedin such an amount to bring the pH to the value of about 4.5, the congreedependent upon the degree of porosity desired, the greater the dilutionthe greater the porosity. The diluted solution may then be afterwardsacidified by further additions of formic acid to a pH value of about 2-3and subsequently allowed to solidify in closed containers. a particularshape is desired in the final mass, the container may take this shape.The gelation or solidification may occur at any desired temperature.After the desired degree of hardness has been obtained, the gel may beremoved from the container and allowed to solidify at a temperature ofabout 20 0., dried at substantially 40 C., and then it may be followedby a drying temperature of 80 C. In those uses, where the presence offree acids or traces of formaldehyde are harmful, the gels may be washedwith diluted ammonia solution either prior or subsequent to the finaldrying. Any excess ammonia or ammonia solution may then be eliminated bydrying at 80 C.

As thus produced, the porous material may then be impregnated with anyexplosive salt and/or oxygen carrier such as ammonium, sodium orpotassium nitrates or the alkali chlorates or perchlorates, and/or suchliquid explosives as nitro-glycerine, nitro-glycols or mixtures thereofwith or without additions of aromatic nitro densation continuing forabout the period of an hour at this pH value. After the condensation iscomplete, the solution may be diluted to a debodies. Obviously suchimpregnation with salts may be in either sufiicient quantity to reducethe absorption of the liquid explosive to the desired value or insuflicient quantity to balance the condensation product with respect tothe oxygen required.

A suitable method of impregnation with salts is to make a solution ofthe latter, 'absorb this solution in theporous material, followed bydrying. Where liquid explosive materials such as nitro-glycerine or thelike are used, they may be absorbed directly in the porous material.Obviously, the proportion of salts or liquid explosives to be combinedwith the porous material may vary within wide limits dependent upon theresult desired, always keeping in mind, however, that the oxygen-carbonbalance must not be unduly disturbed. This is a matter of simplechemical calculation.

Other fillers, such as wood meal, any of the usual vegetable materialheretofore used, or even kieselguhr may be used as admixtures with theabove combinations.

Where porosity is not of great consequence, the final porous materialmay be ground to a desired state of fineness and mixed with the abovesalts or liquid explosives in the desired propor.-'

tions with or without combustible fillers. In some cases, it will befound desirable to use a small quantityof comparatively long fibres suchas bagasse or sisal to act as a binding agent between the particles andassist in making the eventual shape self-sustaining.

In the specification and claims, the term a urea is intended to includeurea, thiourea, substituted urea or thiourea, derivatives thereof,

' mixtures of any of these compounds or any compound which, uponcondensation with formaldehyde or equivalent aldehyde, may produce asuitable porous condensation product.

For the purpose. of this invention, any known process of production maybe used. Furthermore, the combination 'of the before mentionedcondensation with any of the known plastic products such asphenol-formaldehyde condensation products, is not precluded.

While the invention has been described with W here particular referenceto a specific embodiment, it is to be understood that it is not to belimited thereto, but isto be restricted solely by the scope of theclaims.

This application is a continuation in part of the applicants applicationSerial No. 128,985 filed March 4, 1937.

I claim:

1. An explosive comprising a porous condensation product of urea andformaldehyde and an explosive compound contained within its pores.

2. An explosive comprising a porous condensation product of urea andformaldehyde and a solid explosive compound contained within its pores".

3. An explosive comprising a porous condensation product of urea andformaldehyde and a liquid explosive compound contained within its pores.

4. An explosive comprising a porous condensation product of urea andformaldehyde and a solid and liquid explosive compound contained withinits pores.

5. An explosive comprising a porous condensation product of urea andformaldehyde and ammonium nitrate absorbed therein.

6.- An explosive comprising a porous condensation product of urea andformaldehyde and an explosive nitro compound absorbed therein.

7. An explosive comprising a porous condensation product of urea andformaldehyde and nitro-glycerine absorbed therein.

8. An explosive comprising a porous condensation product of urea andformaldehyde and an oxygen carrier and a liquid sensitizer for saidoxygen carrier absorbed therein.

9. The article of claim 1 in which the condensation product is ofnon-uniform porosity.

10. An explosive comprising an integrally formed shape of a porouscondensation product of urea and formaldehyde and an explosive compoundabsorbed therein.

11. An explosive comprising a porous condensation product of a urea andformaldehydeand an explosive compound contained within its pores.

KURT E. RIPPER.

